Method of audio-intonation calibration

ABSTRACT

An audio-intonation calibration method in which an audio signal emitted by a subject is reproduced to the auditory organs of the subject after real time processing, which comprises the following steps: acquisition of a model audio signal to be imitated; spectral analysis of the model audio signal; acquisition of an imitation audio signal emitted by the subject; spectral analysis of the imitation audio signal; comparison of the spectra of the model audio signal and the imitation audio signal; correction of the imitation audio signal as a function of the result of said comparison; and reproduction to the auditory organs of the subject of the corrected audio signal.

The present invention concerns an audio-intonation calibration method.

It also concerns a method of practicing speaking a language beingstudied by a subject and a method of performing a song by a subject.

Generally speaking, the present invention concerns a method in which theemission of an audio signal by a subject is modified by modifying thesound information that he receives when he speaks.

A method of this kind is based on a principle known in the art wherebythe vocal provision of a subject, i.e. sounds that he emits, undergoes amajor transformation as a function of the auditory provision applied tothe same subject, i.e. sound information that he receives.

Using equipment in which an audio signal emitted by a subject isreproduced to the auditory organs of the subject after real timeprocessing is known in the art, and especially in the particular fieldof teaching and practicing speaking languages.

A method of this kind is described in the document WO 92/14229 inparticular.

That document describes a device in which an audio signal emitted by asubject is modified by processing it to take account of thecharacteristics of a foreign language being studied and of the harmoniccontent of that language. The modified audio signal is then furnished tothe subject in real time by a vibratory signal, generally by a soundsignal, in order to modify the audio signal emitted by the subject.

However, in the above document, the audio signal emitted by the subjectis processed in a predetermined manner as a function of the bandwidth ofthe language being learned, and in particular as a function of theenvelope curve of that bandwidth.

In practice, the signal processing circuit comprises a multifrequencyequalizer that is adjusted in a predetermined manner as a function ofthe foreign language in question, and more particularly of the bandwidthof that language and the shape of that bandwidth, i.e. the envelopecurve of the bandwidth. In practice, the equalizer consists of aplurality of successive filters set to different frequencies.

Thus frequency parameters of the equalizer are set in a predeterminedmanner by characteristics of the language being studied.

Similarly, the above document describes a second form of processingapplied to the audio signal emitted by the subject in which adjustmentparameters are established as a function of the sound vibration harmoniccontent of the utterance collected and parameters depending on thelanguage being studied.

In this case, the parameters of a multifrequency equalizer are set bythe difference between the processed signal coming from the effectivevocal provision of the subject and predetermined characteristics of thelanguage.

Thus the above document describes the creation from a first signalrepresentative of the sound emitted by the subject of a second signalmodified with respect to the first signal in a predetermined manner andas a function of the bandwidth of the language being learned, and inparticular as a function of the envelope curve of that language, and athird signal which is derived from the first signal by modifying it as afunction of the effective harmonic content of the utterance andcharacteristics of the language.

The signals are then selectively reproduced to the subject.

The above kind of prior art system has the drawback of using predefinedparameter settings, taking no account of the type of audio signalemitted by the subject.

An object of the present invention is to improve existingaudio-intonation calibration methods in order to simplify their use andwiden their applications.

To this end, the present invention provides an audio-intonationcalibration method in which an audio signal emitted by a subject isreproduced to the auditory organs of said subject after real timeprocessing.

According to the invention, the above method is characterized in that itcomprises the following steps:

-   -   acquisition of a model audio signal to be imitated;    -   spectral analysis of said model audio signal;    -   acquisition of an imitation audio signal emitted by the subject;    -   spectral analysis of the imitation audio signal;    -   comparison of the spectra of the model audio signal and the        imitation audio signal;    -   correction of the imitation audio signal as a function of the        result of said comparison; and    -   reproduction to the auditory organs of the subject of the        corrected audio signal.

By analyzing the frequency content of an audio signal to be imitated andof an audio signal imitated by a subject, the present inventiontransforms the intonation of the person by real time modification of theharmonic content of his utterance and reproduction of the signal thathas been corrected on the basis of the frequency analysis.

Thus the calibration method increases or decreases in real time theintensity of the various frequencies contained in the imitation audiosignal compared to a prerecorded model audio signal.

This kind of calibration method enables the subject to reproduce veryaccurately any type of voice, on the basis of an audio signal to beimitated. Consequently, it finds an application not only in practicingspeaking a foreign language, in which case it is possible to imitateseries of words or phrases pronounced by a native speaker, but also inperforming a song, karaoke style, in which case it becomes possible toreproduce the intonations of a singer when performing a song.

In accordance with preferred features of the invention, the aboveaudio-intonation calibration method further includes the followingsteps:

-   -   measurement of the dynamic range of the audio signal imitated by        the subject;    -   measurement of the dynamic range of the corrected audio signal;    -   comparison of the dynamic range of the imitation audio signal        and the corrected audio signal; and    -   correction of the dynamic range of the corrected audio signal as        a function of the result of said comparison before reproduction        to the auditory organs of the subject of the corrected audio        signal.

In this way it is possible to modify the overall envelope of thecorrected signal as a function of the imitation audio signal to preventthe corrected signal reproduced to the subject having a dynamic rangethat is too different from the audio signal emitted by the subject.

According to preferred features of the invention, the above calibrationmethod further includes a step of storing the spectral analysis of themodel audio signal to be imitated.

Accordingly, it is possible to use the spectral analysis of the modelaudio signal to implement the audio-intonation calibration method whenthe audio signal to be imitated is repeated by a subject after a timedelay.

It is particularly practical, in particular when practicing speaking alanguage, if the audio-intonation calibration method includes a step ofemitting the model audio signal to be imitated into the auditory organsof the subject prior to the step of acquiring the audio signal imitatedby the subject.

Having the subject listen to the signal to be imitated before imitatingit further facilitates practicing speaking a language and improvement ofthe intonation when speaking a word or a phrase in a foreign language.

In a first application of the above audio-intonation calibration method,the present invention provides a method of practicing speaking alanguage being studied, in which method an audio signal emitted by asubject is reproduced to the auditory organs of the subject after realtime processing. This acquisition method uses the audio-intonationcalibration method according to the invention.

Alternatively, in a second application, the present invention alsoprovides a method of performance of a song by a subject, in which methodan audio signal emitted by a subject is reproduced to the auditoryorgans of the subject after real time processing. This method ofperforming a song also uses the audio-intonation calibration methodaccording to the invention.

Finally, the present invention also provides fixed or removableinformation storage means containing software code portions adapted toexecute the steps of the audio-intonation calibration method, of themethod according to the invention of practicing speaking a languagebeing studied, or of the method according to the invention of performinga song.

Other features and advantages of the invention will become more apparentin the course of the following description.

In the appended drawings, which are provided by way of non-limitingexample:

FIG. 1 is an algorithm showing a first embodiment of an audio-intonationcalibration method according to the invention;

FIGS. 2 a, 2 b, 2 c are diagrams showing steps of the audio-intonationcalibration method shown in FIG. 1 or FIG. 5;

FIG. 3 is an algorithm of one embodiment of a method in accordance withthe invention of practicing speaking a language;

FIG. 4 is an algorithm of a calibration step shown in FIG. 3 and FIG. 6;

FIG. 5 is an algorithm of a second embodiment of an audio-intonationcalibration method according to the invention;

FIG. 6 is an algorithm of one embodiment of a method in accordance withthe invention of performing a song; and

FIG. 7 is a block diagram of a computer adapted to implement theinvention.

A first embodiment of an audio-intonation calibration method inaccordance with the invention is described first with reference to FIG.1.

In this example the audio-intonation calibration method is used in amethod of practicing speaking a language.

The invention is based on the fact that each language uses one or morespectral bands with intensities that are specific to it. Thus the ear ofeach subject becomes accustomed to perceiving the spectral fields thatare specific to his native language. Now, the voice reproduces only whatthe ear hears, so that it is difficult for a subject to pronouncecorrectly words in a foreign language when his ear is not accustomed tohearing the fields specific to the new language being studied.

The audio-intonation calibration method according to the inventiontherefore re-educates the ear of a subject by causing the subject tohear in a pronounced manner the fields specific to the language beingstudied.

This method comprises first of all a step E10 of acquiring a model audiosignal to be imitated.

In the case of a foreign language, this audio signal can be a word or aset of words pronounced by a native speaker of the language beingstudied.

A model is preferably acquired from a computer file on which differentmodel audio signals can be stored.

These sound files F can be stored on a computer hard disk or any otherdata medium, such as a CD-ROM, a memory card, etc, or downloaded via acommunication network such as the Internet.

The audio signal to be imitated is then analyzed in a spectral analysisstep E11.

The intensity specific to each of the frequency bands analyzed ismeasured in the analysis step E11.

FIG. 2 a shows one example of the result of this spectral analysis. Theanalysis step E11 is therefore executed over a series of frequency bandswithin the range of audible frequencies from 30 Hz to 10 000 Hz.

The series of frequency bands corresponds to a subdivision of thefrequency range.

In practice, the frequency range is divided into at least 50 frequencybands, and preferably into at least 160 frequency bands, in order toobtain a sufficiently fine analysis of the audio signal.

FIG. 2 a shows this kind of subdivision over a range of frequencies from50 Hz to 1 500 Hz.

Thus the intensity in decibels of each frequency band present in theaudio signal to be imitated can be measured.

In this first embodiment, the result of this spectral analysis (i.e. theanalysis shown in FIG. 2 a in the present example) is stored in a filein a memorization step E12.

The audio-intonation calibration method also includes a step E13 ofacquiring an audio signal imitated by a subject S. In this acquisitionstep E13, an imitation audio signal emitted by the subject S is pickedup via a microphone, for example.

In this embodiment, the dynamic range of the imitation audio signal isfirst measured in a measurement step E14.

The measurement step E14 thus determines the overall envelope of theimitation audio signal.

According to the invention, a spectral analysis step E15 is then appliedto the imitation audio signal.

The spectral analysis step E15 is similar to that previously describedfor the audio signal to be imitated, and analyzes the intensity of theaudio signal recovered in this way from the subject S over a series offrequency bands.

As shown in FIG. 2 b, this provides a spectrum enabling the intensity ofthe signal in each frequency band to be determined over a range offrequencies from 30 Hz to 10 000 Hz.

FIG. 2 b shows one example of this spectrum over the range offrequencies from 50 Hz to 1 500 Hz.

The subdivision into frequency bands is identical to that used in thestep E11 of spectral analysis of the audio signal to be imitated.

The spectra of the model audio signal and the imitation audio signal arethen compared in a comparison step E16.

As shown in FIG. 2 c, the result of this comparison is used in acalculation step E17 to calculate the spectral modifications to be madeto the imitation audio signal.

As shown clearly in FIG. 2 c, and band by band, each frequency band ofthe imitation audio signal is compared with each frequency band of theaudio signal to be imitated, and is corrected so that the intensityvalues of the imitation audio signal correspond to those of the model tobe imitated.

In practice, a correction to be added to or subtracted from the level ofeach frequency band is deduced from this calculation step.

The calculation step therefore defines the modifications to be appliedin each frequency band by adding to or subtracting from the model audiosignal.

The result of the calculation is used to correct the imitation audiosignal in a step E18. In practice, the parameters of a dynamic multibandequalizer are set so that the frequency fields of the imitation audiosignal are equal to those of the acquired model audio signal.

The parameters are set by automatic gain control in each frequency band.

In this preferred embodiment, the dynamic range of the corrected audiosignal after the correction step E18 is measured in order to compare thedynamic range of the imitated signal and the dynamic range of thecorrected audio signal in a comparison step E19.

A calculation step E20 defines the dynamic range modification to beapplied to the signal. The result of this calculation is used to correctthe dynamic range of the corrected audio signal in a correction stepE21.

In practice, the result of the calculation obtained in the calculationstep E20 is used to set the parameters of a variable gain amplifieradapted to adjust the dynamic range of the signal.

The parameters are set by overall automatic gain control.

The calibration method then includes an emission step E22 whichreproduces the corrected audio signal to the auditory organs of thesubject S.

This emission is effected conventionally by means of an amplifier whoseoutput is connected to headphones.

The amplifier enables the subject S to listen selectively either to theimitation audio signal to which the processing previously described hasbeen applied or to the model audio signal acquired in the acquisitionstep E10.

The step of emitting the model audio signal to be imitated into theauditory organs of the subject S is therefore preferably executed beforethe step E13 of acquisition of the imitation audio signal emitted by thesubject S.

A modification step E23 is preferably adapted to modify the model audiosignal to be imitated as a function of parameters representative of alanguage being studied.

In practice, the audio signal to be imitated passes through a presetmultiband graphic equalizer, i.e. an equalizer whose parameters arepreset as a function of a chosen language to accentuate frequency bandsspecific to that language.

In this way, the subject S perceives more clearly the frequency areas inwhich his ears are usually relatively insensitive.

In order additionally to facilitate the work to be done by the subjectS, and in particular the repetition of the audio signal to be imitatedby the subject S, if the audio signal is a text, the method preferablyincludes a step E24 of displaying the text, for example on a screenassociated with the computer.

A method of practicing speaking a language being studied using theaudio-intonation calibration method shown in FIG. 1 is described nextwith reference to FIG. 3.

This method of practicing speaking a language thus improves thepronunciation of a subject S when speaking a chosen language.

The acquisition method shown in FIG. 3 includes first of all acalibration step E30.

This calibration step is shown in FIG. 4.

In its general principle, this calibration step automatically adjuststhe input level of a computer sound card by comparing, before it beginsto be used, the level of a phrase that a subject S pronounces with aprerecorded example.

This calibration enables the student to work autonomously on the methodof practicing speaking, preventing too low or too high sound inputlevels, which could interfere with the correct functioning of themethod.

To this end, this calibration step includes a test step E41 during whichthe subject can decide whether to carry out the calibration or not. Inparticular, if the computer and the associated sound card have just beenused by the same subject, the calibration step can be omitted.

If the calibration is to be carried out, a step E42 of generating anexample generates a reference audio signal.

A display step E43 displays text corresponding to the audio signalgenerated in the generation step E42.

The subject then repeats the audio signal example and his voice isrecorded in a recording step E44.

Comparing the overall intensity of the audio signal example and theaudio signal emitted by the subject in a comparison step E45 enables anintensity level difference between the two audio signals to becalculated in a calculation step E46.

The input gain of the computer sound card is then adjusted in anadjustment step E47.

Returning to FIG. 3, when the calibration step has been executed, aloading step E31 loads software comprising the code of the method ofpracticing speaking a language.

In this embodiment, the same software can be used for differentlanguages.

Of course, separate software could be used for different foreignlanguages.

In this embodiment the required language is chosen in a choice step E32.

The choice step E32 loads into the computer all of the parametersassociated with the language concerned.

In particular, the parameters include one or more frequency spectraspecific to the language being studied.

A particular lesson can be chosen in a second choice step E33.

There can be a plurality of lessons for each language, each lessoncomprising a particular number of prerecorded words or phrases.

The lessons can be graded as a function of a level of languagedifficulties or as a function of different phonemes to be worked on andspecific to each language.

In practice, the parameters and the lesson are loaded conventionallyinto the random access memory (RAM) of the computer.

The acquisition method then includes a step E34 of emitting a phrase ora word to be repeated.

This step of emitting a phrase corresponds to the acquisition step E10and the spectral modification step E23 shown in FIG. 1.

In the emission step E34, the active input of the amplifier is arecording stored in the sound file F.

Thus the emission step E34 enables the subject S to hear an audio signalto be imitated corresponding to a word or a phrase of a text spoken by anative speaker of the language being studied.

The analysis step E11 and the spectral analysis storage step E12 shownin FIG. 1 are executed at the same time.

To facilitate memorization by the subject of the term to be repeated, adisplay step E35 corresponding to the display step E24 shown in FIG. 1is executed at the same time as the step E34 of emitting a phrase.

The acquisition method then includes a time-delay step E36 in which allof the steps E13 to E22 shown in FIG. 1 are executed.

Accordingly, during this time-delay, the subject repeats the audiosignal to be imitated, which is corrected as previously described andreproduced to the ears of the subject in real time, so that the subjectunconsciously and spontaneously modifies his own utterance.

The duration of this time-delay step E36 substantially corresponds tothe duration of the audio signal to be imitated, plus a few seconds toallow the subject to repeat the word or phrase.

The time-delay can be adjustable, for example by the subject, should herequire less time or more time to repeat the various words or phrases.

Progress through the lesson, i.e. through the succession of words to berepeated and the repeated words, can be automatic or manual.

In this embodiment, a test step E37 asks the subject if he wishes towork again on the same phrase or the same word.

If so, the emission step E34, the display step E35, and the time-delaystep E36 are executed on the same audio signal.

If not, a second test step E38 asks the subject if he wishes to workagain on a subsequent phrase or word.

If so, the emission step E34, the display step E35, and the time-delaystep E36 are also executed on a subsequent prerecorded word or phrase inthe current lesson.

Otherwise, the lesson is stopped.

Thus groups of phrases or words can be repeated in looped fashion, thestudent being able to do more or less work on certain parts of thelesson.

After a number of sessions, the ears of the subject become accustomed toperceiving the language and the perception of the new frequency fieldsthat are fed to his ear becomes permanent. The utterance of the subjectis then also permanently modified.

A similar method allowing a subject to execute a song is described nextwith reference to FIGS. 5 and 6.

In this application, the audio-intonation calibration method modifiesthe intonation of a subject in order to adapt his manner of singingoptimally to that of a prerecorded singer.

It therefore enables a subject to sing in the manner of a singer, andcan be used in a karaoke system, for example.

The audio-intonation calibration method in accordance with the inventionis described first with reference to FIG. 5, and is similar to that usedin the FIG. 1 method of practicing speaking a language.

In the present application, the file F is adapted to store one or moresongs. In practice, for each song there are three sound files, onecontaining only the voice of the artist, the other the accompanimentassociated with the song, and the third the text of the song.

As previously, this sound file can be stored on a hard disk of acomputer or on any other data medium (CD-ROM, memory card, etc). It canalso be obtained by downloading it from a communication network such asthe Internet.

Unlike the audio-intonation calibration method shown in FIG. 1 (in whichthe step E10 of acquiring a model and the step E11 of spectral analysisof the model, on the one hand, and the step E13 of recording and thestep E15 of spectral analysis of the imitation audio signal, on theother hand, are carried out alternately, thereby necessitating a stepE12 of storing the spectral analysis of the audio signal to be imitated,for later comparison), here a step E50 of acquiring an audio signal tobe imitated, corresponding to the voice of the singer, is executedsimultaneously with the step E53 of recording the imitation audio signalemitted by the subject S.

As previously, the spectral analysis steps E51 and E55 are applied tothe audio signal to be imitated and to the imitation audio signal,respectively, and the result is fed to the input of a comparator inorder to carry out a spectrum comparison step E56.

The comparison step E56 is followed by a calculation step E57 forcalculating the modifications to be made to the imitation audio signalas a function of the recorded model.

These comparison and calculation steps are similar to those describedwith reference to FIGS. 2 a, 2 b, 2 c.

To obtain a thorough spectral analysis, the frequency range ispreferably divided into at least 160 frequency bands.

The modifications calculated in this way are applied by automatic gaincontrol in each band to modify the imitation audio signal in acorrection step E58.

As previously, the correction can be applied by a dynamically adjustablegraphic equalizer for adjusting the imitation audio signal, frequencyband by frequency band, until it is as close as possible to the acquiredmodel.

Before reproducing the corrected signal to the subject, an envelopemodification step E61 is executed, as previously.

In practice, a step E54 of analyzing the dynamic range of the audiosignal recorded in the recording step E53 provides the overall intensityof the signal. A comparison step E59 compares the dynamic range of therecorded audio signal to the dynamic range of the corrected audio signalin the correction step E58.

A calculation step E60 calculates the modifications to be made to thecorrected audio signal. These modifications are applied by overallautomatic gain control to modify the corrected audio signal in amodification step E61. This envelope modification is effected by meansof a variable gain amplifier.

The audio signal corrected in this way is reproduced to the subject viaan amplifier in an emission step E62.

Accordingly, in this audio-intonation calibration method, the amplifierreceives simultaneously at its input a corrected audio signal and anaccompaniment signal acquired from the sound file F in an acquisitionstep E63.

The subject therefore hears simultaneously the accompaniment and hisvoice as corrected by the processing previously described.

To facilitate the execution of the song, a display step E64 displays thetext simultaneously with the playing of the song.

In practice, and as shown in FIG. 6, this audio-intonation calibrationmethod can be used in a more complex system for karaoke style executionof a song by a subject.

In this method of performing a song, a calibration step E61 can beexecuted before performing a song.

This calibration step corresponds to the calibration step described withreference to FIG. 4 and adjusts the input gain of the computer soundcard.

A loading step E62 is adapted to load software comprising the code ofthe method of performing a song.

A choice step E63 in practice enables the subject to choose a song fromthose stored in the sound file F.

A step E64 of performing the song is then executed as describedpreviously with reference to FIG. 5.

During the playing of a song, the file containing only the accompanimentis fed to the subject S via the amplifier and headphones.

Simultaneously, the text of the song is displayed on the screen of thecomputer in a display step E64. The model file containing the voice isread simultaneously and in perfect synchronization with the filecontaining the accompaniment. The subject also sings simultaneously withthe accompaniment so that the spectral analysis of the two audio signalscan be carried out simultaneously to apply the appropriate modificationsin real time to the imitation audio signal.

To facilitate simultaneity in the interpretation of the song, assistancecan be provided by the emission of a metronome signal and possibly acursor shown on the text of the song to indicate which portion of thetext should be sung.

The perception of the sound he emits as modified in real time causes thesubject to modify the sound he emits unconsciously and also in realtime.

He is therefore caused to sing in the manner of the prerecorded singer.

When the song is finished, a test step E65 enables the subject to chooseto perform the same song again.

If so, the performance step E64 is repeated on the same content of thesound file.

If not, a second test step E66 enables the subject to choose anothersong.

If the subject opts to choose another song, the choice step E63 isrepeated to select one of the prerecorded songs in the sound file.

The performance step E64 is then executed for the new song.

The method of performing a song terminates when no other song isselected after the test step E66.

The audio-intonation calibration method used to perform a song or topractice speaking a language being studied can be implemented on acomputer 10 as shown in FIG. 7.

All of the means employed by the method are incorporated into amicroprocessor (CPU) 11 and a read only memory (ROM) 12 is adapted tostore an audio-intonation calibration program and a program forperforming a song or practicing speaking a language.

A random access memory (RAM) 13 is adapted to store in registers valuesmodified during execution of these programs.

In practice, the RAM comprises registers adapted to memorize the soundfiles F and the spectral analysis results.

The microprocessor 11 is integrated into a computer which may beconnected to a communication network via a communication interface.

The computer further includes means for storing documents, such as ahard disk 14, or is adapted to cooperate with removable document storagemeans, such as disks 5, by means of a disk (floppy disk, compact disk)drive 15, or by means of a computer card.

The fixed or removable storage means can therefore contain the code ofthe audio-intonation calibration method and the code of the method ofpracticing speaking a language or of the method of performing a song.

The code of these methods can be stored on the hard disk of the computer10, for example, and the sound files used in the various applicationscan be stored separately on disks 5 adapted to cooperate with the diskdrive 15.

Alternatively, the program for implementing the invention can be storedin the read only memory 12.

The computer 10 also has a screen 16 providing an interface with thesubject S, in particular to display to the subject the text to berepeated or sung.

A sound card 17 is also provided and is adapted to cooperate with amicrophone 6 and headphones 7 to emit an audio signal or to receive anaudio signal emitted by the subject.

The central processor unit 11 then executes instructions relating toimplementation of the invention. On powering up, the programs andmethods relating to the invention stored in a memory, for example theread only memory 12, are transferred into the random access memory 13,which then contains the executable code of the invention and thevariables necessary to implement the invention.

A communication bus 18 provides communication between various subsystemsthat are part of the computer 10 or connected to it.

The representation of the bus 18 is not limiting on the invention, andin particular the microprocessor 11 could communicate instructions toany subsystem, either directly or via another subsystem.

Thanks to the invention, the audio-intonation calibration method can beimplemented on a personal computer and can be used by a subject Swithout requiring external intervention.

In particular, to practice speaking a language, the subject S can workon his intonation using different prerecorded sound files, withoutnecessitating the presence of a tutor.

Of course, many modifications can be made to the embodiments previouslydescribed without departing from the scope of the invention.

1. An audio-intonation calibration method in which an audio signalemitted by a subject (S) is reproduced to the auditory organs of saidsubject (S) after real time processing, which method is characterized inthat it comprises the following steps: acquisition (E10, E50) of a modelaudio signal to be imitated; spectral analysis (E11, E51) of said modelaudio signal; acquisition (E13, E53) of an imitation audio signalemitted by the subject (S); spectral analysis (E15, E55) of theimitation audio signal; comparison (E16, E56) of the spectra of themodel audio signal and the imitation audio signal; correction (E18, E58)of the imitation audio signal as a function of the result of saidcomparison; and reproduction (E22, E62) to the auditory organs of thesubject (S) of the corrected audio signal.
 2. An audio-intonationcalibration method according to claim 1, characterized in that itfurther includes the following steps: measurement (E14, E24) of thedynamic range of the audio signal imitated by the subject (S);measurement (E18, E28) of the dynamic range of the corrected audiosignal; comparison (E19, E59) of the dynamic range of the imitationaudio signal and the corrected audio signal; and correction (E21, E61)of the dynamic range of the corrected audio signal as a function of theresult of said comparison before reproduction to the auditory organs ofthe subject (S) of the corrected audio signal.
 3. An audio-intonationcalibration method according to either claim 1, characterized in thatthe comparison steps (E16, E56) and correction steps (E18, E58) areexecuted over a series of frequency bands in the range of audiblefrequencies.
 4. An audio-intonation calibration method according toclaim 3, characterized in that the series of frequency bands correspondsto a subdivision of the range of audible frequencies.
 5. Anaudio-intonation calibration method according to either claim 3,characterized in that the range of audible frequencies is divided intoat least 50 frequency bands.
 6. An audio-intonation calibration methodaccording to claim 1, characterized in that the model audio signal to beimitated is a text and in that said method further includes a step (E24,E64) of displaying said text.
 7. An audio-intonation calibration methodaccording to claim 1, characterized in that it further includes a step(E12) of memorizing the spectral analysis of said model audio signal tobe imitated.
 8. An audio-intonation calibration method according to 7claim 1, characterized in that it includes a step (E22) of emitting saidmodel audio signal to be imitated to the auditory organs of the subject(S) before the step (E13) of acquiring the imitation audio signalemitted by the subject (S).
 9. An audio-intonation calibration methodaccording to claim 8, characterized in that it further includes, beforethe emission step (E22), a step (E23) of modifying the model audiosignal to be imitated as a function of parameters representative of alanguage being studied.
 10. An audio-intonation calibration methodaccording to claim 1, characterized in that the model audio signal to beimitated is a song and in that said method further includes,simultaneously with the step (E62) of reproducing the corrected audiosignal to the auditory organs of the subject (S), a step (E62) ofemitting an accompaniment signal of said song to the auditory organs ofthe subject (S).
 11. A method of practicing speaking a language beingstudied, in which method an audio signal emitted by a subject (S) isreproduced to the auditory organs of the subject (S) after real timeprocessing, and which method is characterized in that it uses anaudio-intonation calibration method according to claim
 1. 12. A methodof performance of a song by a subject (S), in which method an audiosignal emitted by a subject (S) is reproduced to the auditory organs ofthe subject after real time processing, and which method ischaracterized in that it uses an audio-intonation calibration methodaccording to claim
 1. 13. Fixed or removable information storage means,characterized in that said means contain software code portions adaptedto execute the steps of an audio-intonation calibration method accordingto claim
 1. 14. Fixed or removable storage means characterized in thatsaid means contain software code portions adapted to execute the stepsof the method according to claim 11 of practicing speaking a languagebeing studied.
 15. Fixed or removable information storage meanscharacterized in that said means contain software code portions adaptedto execute the steps of the method according to claim 12 of performing asong.